Microsoft suspects some PCs might not boot after Windows 11 January 2026 Update

Summary

Microsoft is aware of an alleged issue that leaves PCs unable to boot and requires manual recovery after installing the Windows 11 January 2026 Update. Microsoft doesn’t know how the January 2026 Update broke some PCs and is collecting data from consumers and IT admins. For now, you don’t have to uninstall the update, as the issue is “limited” to specific PCs. The same update also broke Outlook Classic, customization in File Explorer, sleep mode (S3), Citrix Director, and Remote Desktop. “Microsoft has received a limited number of reports of an issue in which devices are failing to boot,” Microsoft noted in a support document first spotted by Windows Latest. It’s unclear how many users are affected, but Microsoft has listed two affected platforms on the Windows release dashboard: KB5074109 – Windows 11 25H2 KB5074109 – Windows 11 24H2 KB5074109 is a mandatory security update for Windows 11 25H2 / 24H2, and it patches as many as a hundred known security issues, which is why it’s installed automatically on PCs. Do I have the January 2026 Update? Open Settings > System > About > Specification, and look at the build number. If it’s 26200.7623, you have the January update. KB5074109 was released on January 13, 2026. According to Microsoft, affected PCs could suddenly stop booting and land on the Black Screen of Death (BSOD) error with stop code UNMOUNTABLE_BOOT_VOLUME. The UNMOUNTABLE_BOOT_VOLUME error (Stop Code 0xED) is typically related to system corruption, a damaged BIOS/boot, or hardware failure, specifically the drive. In this case, Microsoft suspects the problem is likely due to the Windows 11 January 2026 Update. “Microsoft has received a limited number of reports of an issue in which devices are failing to boot with stop code ‘UNMOUNTABLE_BOOT_VOLUME’ after installing the January 2026 Windows security update (the originating KBs listed above), released January 13, 2026, and later updates,” Microsoft explained. “Affected devices show a black screen with the mess...